Existing techniques for identifying noise sources are reviewed. One such technique (the lead-wrapping approach) was used to source-identify a diesel engine and measure the sound power radiated from the major surfaces. Two new advanced techniques (surface intensity and acoustic intensity) were developed and used to measure the sound power radiated from the same major surfaces. The conventional lead-wrapping and new intensity results were compared and agreement was good. The advantages of the new intensity techniques are described and suggestions made for reducing the noise of this and other similar diesel engines.